Yup yup.... 7.5+1= 8.5" which means the centerline is at 4.25" backspace. 44.45mm offset is 1.75 inches. Add the offset to the centerline position and you get 4.25+1.75= 6" backspace.

So there 7.5" wide with 6" backspace.
1" spacer = 5" effective backspace
1.25" spacer = 4.75" effective backspace